The invention relates to an adjusting device for a motor vehicle seat
with a first adjusting arm,
with a second adjusting arm that is arranged opposite the first adjusting arm so as to be rotatable about an axle,
with a drive shaft allocated to the first adjusting arm that has a free end and carries a pinion, and
with a toothed quadrant formed in the second adjusting arm and meshing with the pinion.
Such adjusting devices for vehicle seats are commonly known, they are being used in many different ways.
A motor vehicle seat is kept in a determined adjusting position by means of the adjusting device. If for example the adjusting device is allocated to a height adjusting device of the seat area relative to an underbody, it is responsible for the height position of the seat area and retains for example two adjusting arms in the angular position set by the user. In case of a failure of the adjusting device, if, for example the axle of the pinion breaks or if the pinion disengages from the toothed quadrant, the position of the motor vehicle seat changes. In case of a deceleration of the motor vehicle fitted with the motor vehicle seat in the event of an accident, this may lead to considerable injuries of the occupants. Therefor, the adjusting devices have to be capable of withstanding the high forces occurring during accelerations occasioned by an accident. They should however not be dimensioned with too high cross sections by having for example stability achieved by conferring the different parts the highest possible rigidity, since this increases the overall weight of the motor vehicle seat on one side and on the other makes it stiff so that the frame of the motor vehicle seat itself is no longer capable of reducing kinetic energy in case of an accident.
The object of the present invention is therefore to develop the adjusting devices of the type mentioned above in such a way that, in the case of loads occasioned by an accident, the mesh between pinion and toothed quadrant is kept up even when the pinion and the toothed quadrant are moving against each other.
On the basis of the adjusting device of the type mentioned above, the solution of this object is to have a supporting part formed on the second adjusting arm, wherein said supporting part a) is located in the vicinity of the drive shaft, b) is positioned near the drive shaft radially outside thereof when the pinion is subjected to normal load and c) gets in contact with the drive shaft and supports it when the pinion is subjected to heavy load, particularly when the pinion is subjected to a load occasioned by an accident.
The supporting part on the second adjusting arm effects an abutment for the drive shaft and prevents it from deforming too much under loads occasioned by an accident. Under normal driving conditions, the supporting part does not get in contact with the drive shaft, it is separated therefrom by an air gap. Only when the deformation of the drive shaft and/or of the toothed quadrant has reached a determined degree, the drive shaft gets in contact with the supporting part, thus preventing the pinion from disengaging further from the toothed quadrant. The supporting part thus offers additional safety which is not noticeable under normal driving conditions but which is brought to bear when accelerating forces are established during an accident, in which case it provides an additional support. By dimensioning the different parts, the threshold value that must be reached for the load in order to enable a contact between the drive shaft and the supporting part can be calculated and adjusted. This contact takes place at a time when the relative motion between pinion and toothed quadrant is still far less than the motion required to bring both parts to disengage.
Since, under normal operating conditions of the motor vehicle, the supporting part has no contact with the drive shaft, particular accuracy such as a precise configuration and the like are not necessary. Compared to a second bearing arranged on the free end of the drive shaft, much saving is done while keeping up comparable safety, said saving concerning component parts, assembly expenditures and weight. The free spacing between the drive shaft and the supporting part can be such that strong excursions of the parts of the adjusting device already bring the drive shaft into contact with the supporting part, wherein said excursions are still resilient. It is however also possible and even preferred that the air gap between the supporting part and the drive shaft is only overcome when the deformation of the associated parts is plastic. In this case, the abutment of the supporting part on the drive shaft is at the same time evidence of the necessity to have the corresponding adjusting device and with it the motor vehicle seat either repaired or exchanged depending on the situation.
The arrangement of a supporting part according to the invention permits to provide a support with relatively small mechanical expenditure and possibly without additional weight and additional component parts, said support proving its efficiency even under high acceleration forces as they are occasioned in a rear or in a frontal crash.
In a particularly preferred development, the supporting part is designed as a supporting arch, which exhibits a course that is concentric with the axle of the adjusting device. When the adjusting device is adjusted, the pinion changes its position alongside the toothed quadrant, the position of the axle relative to the second adjusting arm changing at the same time. Thanks to the arch-like shape that has been given to the supporting part, support is obtained for any position of the axle relative to the second adjusting arm.
In a particularly preferred embodiment, the drive shaft is connected with a disk in the vicinity of the pinion, said disk being located near the supporting part when the pinion is subjected to a normal load and getting in contact with the supporting part on which it rests when the pinion is subjected to heavy load, particularly when it is subjected to load in the event of an accident. This disk provides additional safety. The disk can be so big and be arranged on the free end of the drive shaft so that axial movement of the second adjusting arm away from the first adjusting arm is hindered. The reverse motion, that is the movement of the second adjusting arm toward the first adjusting arm, is limited by causing both arms to hit against each other. As a result, the second adjusting arm cannot move so far away from the first adjusting arm and thus from the pinion that the pinion axially disengages from the toothed quadrant.
In a preferred embodiment the toothed quadrant is formed on the edge of an arched oblong hole in the second adjusting arm. On the second adjusting arm, a supporting arch protrudes on said oblong hole and completely encircles it. This arch supports the axle and in particular the disk across the longitudinal direction of the toothed quadrant and the direction of the axle.